Effects of spin fluctuation on the magnetic anisotropy constant of itinerant electron magnets

Abstract

In the disordered local moment picture, we calculated the magnetization (M ) and magnetic anisotropy energy (MAE) of FePt, CoPt, and MnAl ordered alloys and body-centered tegragonal FeCo (bct-FeCo) disordered alloy, assuming spatially fluctuated spin configurations at finite temperatures. All alloys exhibit the relationn with the exponent n ≈ 2. This is consistent with the two-ion anisotropy model, in contrast to the usual singleion anisotropy model exhibiting n = 3. Because these systems have different mechanisms of MAE, we suggest that this relation is a general rule for itinerant electron systems.

Monte Carlo analysis for finite-temperature magnetism ofNd2Fe14Bpermanent magnet

“…Therefore, it is natural that multi-sublattice model such as Nd 2 Fe 14 B does not follow the Callen-Callen law, which was also pointed out by using a mean field approach. 49 Additionally, in actual ferromagnetic metals that have two-ion magnetic anisotropy, the temperature dependence of magnetic anisotropy deviates from Callen-Callen law, 19,[50][51][52][53] such as L1 0 -FePt, K A 1 (T ) ∝ M 2.1 (T ). 51 Therefore, more detailed discussion of the temperature dependence is needed to formulate the theory for itinerant electrons and inhomogeneous systems.…”

Магнитокристаллическая анизотропия спеченных магнитов (PrDy)(FeCo)B

“…В [6] было установлено, что для сплавов PtCo, PdFe и PtFe температурное поведение анизотропии можно описать с помощью двухподрешеточной модели (в отличие от одноподрешеточной модели в теории Callen−Callen). Авторы [10] получили линейную зависимость магнитной анизотропии от намагниченности насыщения со значением m = 1.9−2.1 для сплавов FePt, CoPt, MnAl, FeCo. Закон Callen−Callen может также нарушаться в случае, когда имеются атомы с сильной спин-орбитальной связью, которые вносят вклад в анизотропию, но не оказывают заметного влияния на другие магнитные свойства [6,8,11,12].…”

Study of ground state magnetic structure of L10-type MnAl via spin-spiral density wave

“…The material has a long history 1,2) and has been extensively researched from both experimental and theoretical aspects. From the point of view of theoretical aspects, many theoretical studies [3][4][5][6][7][8] have been performed with the density functional theory (DFT) to investigate the electronic structure and magnetic properties of MnAl, not only at 0 K but also at finite temperatures. In these works, the ferromagnetic phase was assumed for the magnetic ground state of MnAl, however, the magnetic structure of MnAl in the ground state remains controversial.…”